I. Field of the invention
The present invention relates generally to semiconductor integrated devices and, more particularly, to a method for fabricating Zener diodes in said devices.
II. Description of the related art
Smart power integrated circuit (IC) transistors generally combine logic and power transistor devices on the same semiconductor chip. Such smart power ICs are fabricated by Texas Instrument's Inc., according to a novel multi-epitaxial linear process. The power and logic devices included on these ICs are circuit connected to provide desired operating functions. An example of one such circuit is the high-side driver. High-side drivers are often expected to deliver considerable amounts of drive current to external loads. When used in the automotive industry, such loads typically include lamps, motors, transformer primaries, and other forms of inductive loads.
There are numerous advantages to having an integrated high-side driver. Having control circuitry on board with the power circuitry allows for easy current and temperature sensing for self protected devices. The ICs can also incorporate protection from reverse battery conditions, lost of battery and other conditions which previously had to be dealt with externally. Even with the above benefits such circuits are deficient in their ability to drive inductive loads. A specific problem is that, when driving inductive loads, any interruption in drive current will cause the output structure to develop Vce voltages which may exceed the IC device rating. As a result, the power transistor may be destroyed by driving it into secondary breakdown. Thus it is apparent that a transient protection mechanism for preventing potential destruction of the device in a shorted load or a transient load condition is desired.
To be most beneficial the incorporation of such mechanism should be completely compatible with the process for fabricating the integrated circuit in order to achieve full integration on the chip. Such mechanism should have versatility in its voltage handling characteristics in order to allow for design flexibility of the IC. Additionally, such mechanism should be manufacturable in different embodiments to allow even greater design flexibility.